Immunologic mechanisms may be important in ocular tumors. We have previously demonstrated cellular reactivity towards melanoma-associated antigens in patients with choroidal melanoma. Studies are ongoing to determine whether the use of highly purified melanoma-associated antigens in in vitro assays will allow us to better predict which patients with choroidal melanoma are at greater risk of developing metastatic disease. In retinoblastoma we have demonstrated the existence of immune complexes. Current work is being performed to determine the nature of the antigen and antibody moieties which make up the immune complexes. Serial studies are being performed on retinoblastoma patients to determine whether immune complex levels will correlate with disease status and prognosis. In patients with orbital pseudotumors and lymphomas, the histologic diagnosis is inaccurate in up to 50 percent of cases. Using lymphocyte surface markers studies, we may be better able to differentiate these two types of orbital mass lesions which have a markedly different prognosis. Studies are ongoing on the specificity, sensitivity, and reproducibility of immunologic lymphocyte surface marker studies in patients with ocular disease.